SHOOT GROWTH, RADIATION INTERCEPTION AND DRY-MATTER PRODUCTION AND PARTITIONING DURING THE ESTABLISHMENT PHASE OF MISCANTHUS-SINENSIS GIGANTEUS GROWN AT 2 DENSITIES IN THE UK

Photosynthetic area index (PAI), radiation interception (I) and dry matter partitioning between shoots and roots were measured for Miscanthus sinensis 'Giganteus' grown from micro-propagated transplants on a fertile peaty loam soil in eastern England. In the establishment year, Miscanthus plants produced 35 and 70 shoots plant(-1) at densities of 4.0 and 1.8 plants m(-2) respectively. At the higher density, there were 140 shoots m(-2) with the largest reaching a height of 1.8 m; these canopies attained a maximum PAI of 5.45, intercepting 94% of incident radiation. Leaf lamina contributed c. 90% of total photosynthetic area with stems contributing the remainder. At the lower density, maximum PAI and I values were 2.88 and 86% respectively. PAI was related to I by calculating attenuation coefficients (k); these indicated that Miscanthus canopies were more effective at intercepting radiation per unit PAI at the lower density (k = -0.31) compared with the higher density (k = -0.20). Radiation interception was related to dry matter accumulated by calculating conversion efficiencies (epsilon). At 4 plants m(-2), epsilon for shoot dry matter production was 1.17g MJ(-1) Miscanthus partitioned a relatively large amount of total dry matter into below-ground biomass. By plant senescence, c. 30% of total dry matter had been partitioned into root and rhizome; rhizome biomass contributed 80% of below-ground dry matter. epsilon increased to 1.62 g MJ(-1) when calculated on a total dry matter basis (shoot + root + rhizome). Total dry matter production was increased 68% by a 2.2-fold increase in plant density.